STHS Computer Technology

On the breadboard, construct two bi-directional motor control circuits, commonly referred to as "H-bridge" circuits. These circuits will manage the two DC motors that propel the wheels. Each circuit will have two wires connected to the Arduino (one for forward movement and one for backward movement) to control the circuit, along with two wires connected to the respective DC motor being controlled. It is essential to test the circuits to confirm that both motors can be operated in both forward and reverse directions. A sample Arduino sketch is provided for testing the motors. The code should be modified to verify each motor's operation and direction, and the circuit should be inspected for any motor that does not perform as expected. Additionally, a schematic circuit diagram is available for one QRD line sensor connected to the Arduino. Since two sensors will be wired, the robot will be able to detect whether it is on the line, slightly off to the left, slightly off to the right, or completely off the line. It is important to test both QRD1114 sensors to ensure they are functioning correctly and sending accurate signals to the Arduino. A sample Arduino sketch is also provided for testing the circuits. Ensure that a good range of values is obtained from both sensors, differentiating between light and dark. Record the highest and lowest values obtained from each sensor, as the midpoint of these values will serve as the "cut off" or "threshold" value, which will be used to determine if the sensor detects the dark line.

To create an effective H-bridge circuit for controlling DC motors, it is essential to understand the basic configuration and operation of the components involved. An H-bridge consists of four switches (transistors or MOSFETs) arranged in an "H" shape, allowing current to flow in either direction through the motor, thus enabling forward and reverse rotation.

In this setup, the Arduino will control the H-bridge by sending signals to the gates of the transistors. When one pair of transistors is activated, the motor will rotate in one direction, while activating the other pair will reverse the motor's direction. The control signals can be generated using digital output pins from the Arduino, with one pin dedicated to each direction of the motor.

For the QRD line sensors, the circuit typically includes an infrared LED and a phototransistor. The LED emits infrared light, which reflects off the surface below it. The phototransistor detects the reflected light. When the sensor is over a dark line, less light is reflected, resulting in a lower signal at the phototransistor's output. Conversely, when the sensor is over a lighter surface, more light is reflected, yielding a higher output signal.

To ensure reliable operation, the Arduino must read the sensor values and establish a threshold. By determining the highest and lowest values from the sensors, the midpoint can be calculated and used as the threshold value. This threshold will allow the robot to make decisions based on the sensor readings, enabling it to follow the line accurately.

Testing of both the H-bridge circuits and the QRD line sensors is crucial. For the motors, the Arduino sketch should be modified to test each motor's functionality in both directions, ensuring proper operation. For the QRD sensors, the Arduino should continuously read values and compare them against the established threshold to maintain accurate line following behavior. Proper calibration and testing will ensure the robot performs as intended, effectively navigating its environment.On the breadboard, build two bi-directional motor control circuits (also known as "H-bridge") circuits. These circuits will control the two DC motors that drive the wheels. Each circuit will have two wires from the Arduino (one for forward, one for backward) to control the circuit, and two wires from the single DC motor that it is controlling.

You should test your circuits to ensure you can control both motors in both forward and reverse directions. Here is a sample Arduino sketch you can use to test the motors. Edit the code to check each motor and direction, and double-check the circuit for any motor that doesn`t behave as expected.

Here`s the schematic circuit diagram of one QRD line sensor connected to the Arduino. You will be wiring two of these, so your robot can tell whether it is on the line, off a little bit to the left, off a little bit to the right, or completely off the line. Now test that both QRD1114`s are operating correctly, and sending a proper signal to the Arduino. Here is a sample Arduino sketch to test the circuits. Make sure you are getting a good range of values from both sensors between light and dark. Make a not of the highest and lowest values you get from each sensor. You will use a value half way in between these for your "cut off" or "threshold" value. This is the boundary value we`ll use to decide if the sensor is seeing the dark line or not. 🔗 External reference